A.
Always chew and swallow all the food in your mouth before taking more or taking a drink.
B.
You may eat chicken and pizza with your fingers if you are at a barbecue, finger buffet or very informal setting. Otherwise always use a knife and fork.
C.
It is polite to start eating before everyone has been served unless your host says that you don't need to wait.
D.
Always say thank you when served something. It shows appreciation.